1. Field of the invention
This invention relates to the atomization of liquids by means of a piezoelectric vibrator and more specifically it concerns novel methods and apparatus for controlling such atomization in an efficient and effective manner.
The present invention also relates to means for the distribution of a liquid active material, such as a perfume, air freshener, insecticide formulation, or other material, in the form of fine particles or droplets, as in a fine spray, by means of a piezoelectric device. In particular, the invention is directed to a piezoelectric liquid delivery system for production of droplets of liquid, or liquid suspensions, by means of an electromechanical or electroacoustical actuator. Even more specifically, the present invention relates to an improved control circuit for use with such devices.
2. Description of the Related Art
The use of piezoelectric vibrators to atomize liquids is well known; and examples of such devices are described in U.S. Pat. Nos. 5,164,740, 4,632,311 and 4,533,082. In general, these devices apply an alternating voltage to a piezoelectric element to cause it to expand and contract. The piezoelectric element is coupled to a perforated membrane, which in turn is in contact with a liquid source. The expansion and contraction of the piezoelectric element causes the membrane to vibrate up and down whereupon liquid is driven into the membrane""s perforations and is then thrown upwardly in the form of a fine mist.
It is desired to provide a battery driven piezoelectric atomizer which operates over a long period of time without deterioration of its performance and which permits the use of inexpensive alkaline batteries whose voltage output is known to decrease over the operating life of the battery.
One way in which a piezoelectric atomizer can be drive n economically is to control it to operate during drive periods which are separated by sleep periods, so that liquid becomes atomized during the drive periods in successive short puffs. However, during the sleep periods between puffs, liquid accumulates on the membrane; and in order to start a successive puff at the next drive period, the membrane must be driven at a large amplitude.
Another way in which a battery operated piezoelectric atomizer can be operated economically is to drive it at the resonant frequency of its vibrating system, which includes the membrane, the piezoelectric element and any mechanical coupling between the membrane and the element. A problem occurs, however, because the resonant frequency may vary somewhat from device to device so that a different driving frequency must be set for each unit.
The distribution of liquids by formation of a fine spray, or atomization, is well known. One method for such distribution is to atomize a liquid by means of the acoustic vibration generated by an ultrasonic piezoelectric vibrator. An example of such a method is shown in U.S. Pat. No. 4,702,418, which discloses an aerosol dispenser including a nozzle chamber for holding fluid to be dispensed and a diaphragm forming at least a portion of the chamber. An aerosol dispensing nozzle is disposed therein, with a restrictive passage for introducing liquid from the reservoir to the nozzle. A pulse generator in combination with a low voltage power source is used to drive a piezoelectric bender, which drives fluid from the reservoir through the nozzle to create an aerosol spray.
Another atomizer spraying device is shown in U.S. Pat. No. 5,518,179, which teaches a, liquid droplet production apparatus comprising a membrane which is vibrated by an actuator which has a composite thin-walled structure, and is arranged to operate in a bending mode. Liquid is supplied directly to a surface of the membrane and sprayed therefrom in fine droplets upon vibration of the membrane.
U.S. Pat. Nos. 5,297,734 and 5,657,926 teach ultrasonic atomizing devices comprising piezoelectric vibrators with a vibrating plate connected thereto.
In U.S. Pat. No. 5,297,734, the vibrating plate is described as having a large number of minute holes therein for passage of the liquid.
While a number of additional patents disclose means for the dispersion of liquids by ultrasonic atomization, or for timed intervals of dispersion, they have achieved only moderate success in the efficient atomization of such materials as perfumes. See, e.g., U.S. Pat. Nos. 3,543,122, 3,615,041, 4,479,609, 4,533,082, and 4,790,479. The disclosures of these patents, and of all other publications referred to herein, are incorporated by reference as if fully set forth herein.
Such atomizers fail to provide an easily portable, battery operated dispenser employing an orifice plate in mechanical connection with a piezoelectric element, capable of long periods of use with little or no variation in the delivery rate. Furthermore, the efficiency of these atomizers may differ due to manufacturing differences in the atomizer piezoelectric pump components. Thus, a need exists for improved atomizers or dispensers for use in distribution of active fluids such as fragrances and insecticides, which atomizers are highly efficient and consume minimal electrical power while providing wide dispersal of the liquid.
The present invention in is various aspects, overcomes the above problems.
In one aspect, the present invention involves a novel method for operating a vibratory liquid atomizer of the type in which a membrane, to which liquid to be atomized is supplied, vibrates to drive the liquid from its surface in the form of a mist. This novel method includes the steps of initially vibrating the membrane at a high amplitude to initiate atomization of the liquid: and thereafter vibrating the membrane at a lower amplitude sufficient to sustain the atomization.
In another aspect, the invention involves a novel method for operating a piezoelectric vibratory liquid atomizer of the type in which a piezoelectric actuating element is energized by an alternating voltage to expand and contract and thereby to vibrate a membrane, to which a liquid to be atomized is supplied, so that the vibration of the membrane atomizes said liquid and ejects it from the membrane in the form of a mist. This novel method comprises the steps of first applying a high alternating voltage to said the piezoelectric actuating element to cause it to vibrate the membrane at a high amplitude to initiate atomization of the liquid; and thereafter applying a lower alternating voltage to the piezoelectric actuating element to sustain atomization.
In a further aspect the invention involves a novel vibratory liquid atomizer which comprises a membrane, a liquid conduit which is arranged to supply liquid to be atomized to the membrane, and a vibration actuator connected to first vibrate the membrane during a drive period at a high amplitude to initiate atomization of the liquid and thereafter, during the same drive period, to vibrate the membrane at a lower amplitude sufficient to sustain the atomization.
In a still further aspect, the present invention involves a novel vibratory liquid atomizer which comprises a membrane mounted which is mounted to be vibrated, a liquid supply conduit arranged to supply liquid to the membrane while it is vibrating, a piezoelectric actuating element coupled to the membrane to cause it to vibrate when the piezoelectric element expands and contracts, and an electric power supply system connected to supply an alternating voltage to the actuating element during a drive period to cause it to expand and contract and thereby to vibrate the membrane to atomize the liquid and eject it in the form of a mist. The electric power supply system includes circuits which are connected to first apply a high alternating voltage to said the piezoelectric actuating element to cause it to vibrate the membrane at a high amplitude to initiate atomization of the liquid and thereafter to apply a lower alternating voltage to the piezoelectric actuating element to sustain atomization.
A primary purpose of the present invention is to provide, a highly efficient method for dispensing such liquids as perfumes, air fresheners, or other liquids. Such other liquids include household cleaning materials, sanitizers, disinfectants, repellants, insecticides, aroma therapy formulations, medicinals, therapeutic liquids, or other liquids or liquid suspensions which benefit from atomization for use. These compositions may be aqueous, or comprise various solvents.
It is an object of the present invention to provide improved control circuits for use with an easily portable, battery operated dispenser employing a domed Orifice plate in mechanical connection with a piezoelectric element. The piezoelectric pump is capable of operating efficiently for months, on low voltage batteries, while maintaining consistency of delivery throughout the period. A piezoelectric atomizer is capable for use with such electrical sources as 9 volt batteries, conventional dry cells such as xe2x80x9cAxe2x80x9d, xe2x80x9cAAxe2x80x9d, xe2x80x9cAAAxe2x80x9d, xe2x80x9cCxe2x80x9d, and xe2x80x9cDxe2x80x9d cells, button cells, watch batteries, and solar cells. The preferred energy sources for utilization in combination with the present invention are xe2x80x9cAAxe2x80x9d and xe2x80x9cAAAxe2x80x9d cells.
The piezoelectric pump has circuitry to compensate for manufacturing differences in the pump components. The electronics of such circuitry may be programmable, and may be used to set a precise delivery rate (in milligrams per hour, hereinafter mg/hr). Alternatively, the electronic circuitry may allow the consumer to adjust intensity or effectiveness to a desired level for personal preference, efficacy, or for room size.
In the preferred embodiment of the present invention, these and other objects of this invention are achieved by an atomizer for fragrances, insecticide formulations, and other liquids such as set forth previously, wherein the atomization system includes a chamber for the liquid to be dispensed, means to supply the liquid from said chamber to an orifice plate for dispersal of the liquid, a piezoelectric element, an energy source, and the improved circuitry to drive and control the piezoelectric element. It has been found that by controlling the amplitude and frequency of the signal driving the piezoelectric element, superior results are attained. The present invention thus provides a means for more uniform atomization of the liquid to be dispensed throughout the total period of dispersion, such that the amount dispersed per time unit at the commencement of dispersion does not vary as greatly from the amount dispersed near or at the finish of dispersion. These and still other objects and advantages of the present invention will be apparent from the description which follows, which is, however, merely of the preferred embodiments. Thus, the claims should be looked to in order to understand the full scope of the invention.
The invention also involves other specific features which are described hereinafter; and which in combination with the foregoing features, provide additional advantages.